Remaining toner conveying apparatus and image forming apparatus

ABSTRACT

Provided is a remaining toner conveying apparatus including a cleaning blade which recovers a toner remaining on a surface of a photosensitive drum and a conveying screw which conveys the remaining toner so that a conveyance amount per predetermined time in a first conveyance path conveying the remaining toner recovered by the cleaning blade to a discharge portion for discharging the remaining toner is equal to or less than a conveyance amount in a second conveyance path in a downstream side in a conveyance direction where the conveyance path is narrower than the first conveyance path.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a remaining toner conveying apparatus providedin an image forming apparatus such as a printer, a copying machine, afacsimile machine, and the like.

Description of the Related Art

In an image forming apparatus, an electrostatic latent image is formedby exposing a surface of a photosensitive drum (image bearing member)uniformly charged by a charging device with laser beam corresponding toimage information. After that, a developer (toner) is supplied to theelectrostatic latent image formed on the surface of the photosensitivedrum by the developing device to develop the electrostatic latent imageas a toner image. Next, the toner image formed on the surface of thephotosensitive drum is transferred onto a recording material such as asheet by a transfer device.

At this time, all of the developer does not move from the surface of thephotosensitive drum to the recording material by the transfer device,but some of the developer remains on the surface of the photosensitivedrum. Such residual developer is recovered from the surface of thephotosensitive drum by the cleaning device. Such a developer is referredto as a transfer residual toner, a remaining toner, or the like.Hereinafter, the developer remaining on the surface of thephotosensitive drum after the transfer is referred to as remainingtoner.

The remaining toner is recovered by the cleaning device and then storedin the remaining toner container provided in a drum cartridge.Alternatively, in general, the toner is temporarily stored in aremaining toner container and then conveyed into a remaining tonercontainer different from the drum cartridge by a conveying portion suchas a conveying screw to be stored.

In the configuration of the remaining toner container attached to thephotosensitive drum, the remaining toner on the surface of thephotosensitive drum is temporarily stored in a remaining tonercontaining portion adjacent to the photosensitive drum. Until the toneris discharged to the outside by the conveying portion provided insidethe remaining toner containing portion, the remaining toner convects inthe space formed between the photosensitive drum and the conveyingportion due to the rotational force of the photosensitive drum.

Some of the developer contain abrasives for the purpose of activelyscraping (polishing) the surface of the photosensitive drum. In the caseof using such a developer, the remaining toner temporarily convectingdue to the rotational force of the photosensitive drum in the spaceformed between the photosensitive drum and the conveying portion is incontact with the surface of the photosensitive drum and, thus, activelyscrapes off the surface of the photosensitive drum.

The polishing of the surface of the photosensitive drum has the effectof suppressing the occurrence of image defect called image flow causedby electric discharge products adhered by an electric dischargephenomenon of a charging device. In order to electrically charge thesurface of the photosensitive drum, the charging device is required tocause the electric discharge phenomenon in the vicinity of the chargingdevice. It is known that, if such an electric discharge phenomenonoccurs, the bonding state of the elements in the air changes, and anelectric discharge product called NOx is generated.

If the electric discharge product absorbs moisture in such a state thatthe electric discharge product is adhered and accumulated on the surfaceof the photosensitive drum, the resistance of the surface of thephotosensitive drum is lowered. If the surface of the photosensitivedrum in a state of lowered resistance is irradiated with a laser beam,an electrostatic latent image is formed on the surface of thephotosensitive drum. In this case, the boundary between the irradiatedportion of the laser beam and the non-irradiated portion of the laserbeam becomes ambiguous.

As a result, the electrostatic latent image becomes blurred. Thisphenomenon is called image flow. In order to suppress the occurrence ofsuch image flow, it is necessary to increase the convection performanceof the remaining toner in the vicinity of the opening of the remainingtoner container facing the surface of the photosensitive drum and topolish the surface of the photosensitive drum by using an abrasivecontaining in the remaining toner.

JP 2015-028509 discloses prevention of image flow and recoveryoperation. JP 2015-028509 discloses a technique of detecting a densitydetection pattern formed on the surface of the photosensitive drum by adensity sensor and polishing the surface of the photosensitive drum byan idling rotation operation or the like based on a change in density.In the idling rotation operation of JP 2015-028509, the polishing effectfor the surface of the photosensitive drum by the cleaning blade isexpressed.

In addition, in some cases, if the convection performance of theremaining toner in the vicinity of the opening of the remaining tonercontainer facing the surface of the photosensitive drum is poor, paperdust contained in the remaining toner is separated in the vicinity ofthe remaining toner containing portion, and a paper dust layer(hereinafter, referred to as a “paper dust net”) may be formed wherepaper dust is laminated in the vicinity of the opening. In some cases,such a paper dust net is sandwiched between a cleaning blade and thesurface of the photosensitive drum, and thus, cleaning defect may occur.The occurrence of the paper dust net is suppressed by the increase inthe convection performance of the remaining toner in the vicinity of theopening of the remaining toner container facing the surface of thephotosensitive drum.

However, in the remaining toner conveying apparatus disclosed in JP2015-028509, if a conveying speed is slowed in order to improve theconvection performance of the remaining toner, the remaining toner isclogged in the vicinity of the discharge portion of the remaining toner.In addition, the rotation of a conveying member is hindered, and thus,there is a problem in that the conveying member is damaged.

SUMMARY OF THE INVENTION

A representative configuration of a remaining toner conveying apparatusaccording to the present invention includes: an introducing portionconfigured to introduce a developer remaining on an image bearing memberwithout being transferred; and

a conveying portion configured to convey the developer introduced by theintroducing portion toward a discharge portion, the conveying portionconveying the developer so that a conveyance amount of the developer perpredetermined time in a first conveyance path is equal to or less than aconveyance amount per the predetermined time of the developer in asecond conveyance path which is in a downstream side of the firstconveyance path in a direction of the conveying and narrower than thefirst conveyance path.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory cross-sectional diagram illustrating aconfiguration of an image forming apparatus according to the invention.

FIG. 2 is an explanatory cross-sectional diagram illustrating aconfiguration of a remaining toner conveying apparatus according to thefirst embodiment.

FIG. 3 is an explanatory perspective diagram illustrating aconfiguration of the remaining toner conveying apparatus according tothe first embodiment.

FIG. 4 is a cross-sectional view taken along line G-G in FIG. 2.

FIG. 5 is a cross-sectional view taken along line H-H of FIG. 2.

FIG. 6 is an explanatory front diagram illustrating a configuration of aconveying screw according to the first embodiment.

FIG. 7 is a diagram illustrating a result of comparison of conveyingforces of remaining toner according to a difference in outer diameter ofspiral blades of a conveying screw.

FIG. 8 is an explanatory front diagram illustrating a configuration of aconveying screw according to a second embodiment.

FIG. 9 is a diagram illustrating a result of comparison of conveyingforces of remaining toner according to a difference in separationpitches of spiral blades of the conveying screw in a rotation shaftdirection according to the second embodiment.

FIG. 10 is an explanatory front diagram illustrating a configuration ofa conveying screw according to a third embodiment.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of an image forming apparatus provided with a remainingtoner conveying apparatus according to the invention will be describedspecifically with reference to the drawings.

First Embodiment

First, a configuration of a first embodiment of the image formingapparatus provided with the remaining toner conveying apparatusaccording to the invention will be described with reference to FIG. 1 toFIG. 7.

<Image Forming Apparatus>

First, a configuration of the image forming apparatus 7 according tothis embodiment will be described with reference to FIG. 1. FIG. 1 is anexplanatory cross-sectional diagram illustrating a configuration of theimage forming apparatus 7 according to this embodiment. The imageforming apparatus 7 illustrated in FIG. 1 is configured as a copyingmachine, a printer, a facsimile apparatus, or a multifunction peripheralhaving at least two of these functions.

In the image forming apparatus 7 illustrated in FIG. 1, a photosensitivedrum 1 serving as an image bearing member configured as a drum-shapedphotosensitive member is rotatably supported around a rotation shaft 1a. With the start of an image forming operation, the photosensitive drum1 is rotationally driven in the direction of the arrow A in FIG. 1 bythe motor 22 as a driving source illustrated in FIG. 2.

The surface of the photosensitive drum 1 rotating in the direction ofthe arrow A in FIG. 1 is uniformly charged to a potential of apredetermined polarity by the charging roller 3 serving as a chargingportion. The charging roller 3 according to this embodiment is aconductive elastic roller having a core metal having conductivity as aroller shaft body (support body) 3 a. Then, both ends of the rollershaft body 3 a are rotatably supported through respective bearingmembers. The axis line of the roller shaft body 3 a is arrangedsubstantially in parallel to the axis line of the rotation shaft 1 a ofthe photosensitive drum 1, and the charging roller is in contact withthe photosensitive drum 1 with a predetermined pressing force.

When the photosensitive drum 1 rotates in the direction of the arrow Ain FIG. 1, the charging roller 3 rotates in the direction of the arrow Bin FIG. 1 by a motor serving as a driving portion (not illustrated) orrotates in the direction of the arrow B in FIG. 1 by following themovement of the surface of the photosensitive drum 1. And when thecharging roller 3 rotates in the direction of the arrow B in FIG. 1, apredetermined DC voltage (DC charging method) from a charging bias powersupply (not illustrated) or a voltage obtained by superimposing apredetermined AC voltage on a predetermined DC voltage (AC+DC chargingmethod) is applied as a charging bias. As a result, the surface of thephotosensitive drum 1 rotating in the direction of the arrow A in FIG. 1is uniformly charged to a potential of a predetermined polarity in acontact manner.

The surface of the uniformly charged photosensitive drum 1 is irradiatedwith light-modulated laser beam 12 emitted from a laser writing portion(not illustrated) serving as an image exposing portion to be exposed. Asa result, an exposure bright portion of the surface of thephotosensitive drum 1 is attenuated in potential, so that anelectrostatic latent image corresponding to an image exposure pattern isformed. The image exposing portion may be an analog exposure apparatuswhich capture, projects, and exposes an image of an original or may be adigital exposure apparatus such as a laser scanner or a light emittingdiode (LED) array.

The electrostatic latent image formed on the surface of thephotosensitive drum 1 is supplied with a toner (developer) from adeveloping device 6 serving as a developing portion to be developed as atoner image. The developing device 6 according to this embodimentemploys a jumping reversal developing device using a one-componentmagnetic toner having negative polarity as a developer. The developingdevice 6 is configured to include a developing sleeve 5 serving as adeveloper bearing member which is a rotatably driven and a hopper (notillustrated) which supplies the developer to the developing sleeve 5.The developing sleeve 5 and the surface of the photosensitive drum 1 arearranged so as to maintain a constant interval in the longitudinaldirection of the photosensitive drum 1.

A voltage obtained by superimposing a predetermined AC component and aDC component from a developing bias power supply (not illustrated) isapplied to the developing sleeve 5. As a result, the electrostaticlatent image formed on the surface of the photosensitive drum 1 issupplied with the toner through jumping reversal by the developingdevice 6 to be developed as a toner image.

On the other hand, a recording material 21 is fed from a feeding unit(not illustrated), and the recording material 21 is conveyed to atransfer nip portion between the surface of the photosensitive drum 1and a transfer roller 9 serving as a transfer portion arranged to facethe photosensitive drum 1. A transfer voltage is applied from a transferbias power supply (not illustrated) to the transfer roller 9. As aresult, the toner image formed on the surface of the photosensitive drum1 is electrostatically transferred onto the recording material 21. Inaddition, in some configurations, the toner image formed on the surfaceof the photosensitive drum 1 may be primarily transferred onto anintermediate transfer member (not illustrated), and the toner imageprimarily-transferred onto the intermediate transfer member may besecondarily transferred onto the recording material 21.

The transfer residual toner 8 a adhering to the surface of thephotosensitive drum 1 after the transfer of the toner image to therecording material 21 is scraped off by the cleaning blade 2(introducing portion) serving as a cleaning portion pressed against thesurface of the photosensitive drum 1 to be removed. The cleaning blade 2is arranged along the longitudinal direction of the photosensitive drum1 over the entire area of the image forming region R1 on the surface ofthe photosensitive drum 1.

The remaining toner 8 b removed by the cleaning blade 2 is recoveredinto the conveyance path 11 from the opening 11 a of the conveyance path11 arranged along the longitudinal direction of the photosensitive drum1. After that, the remaining toner is conveyed in the conveyance path 11by the conveying screw 10 rotatably supported in the conveyance path 11and is discharged from a discharge outlet 11 c of the discharge portion11 b provided at one end of the conveyance path 11 in the longitudinaldirection thereof illustrated in FIGS. 2 and 3. The conveying screw 10is arranged along the longitudinal direction of the photosensitive drum1. As illustrated in FIG. 2, the conveying screw 10 is configured tohave a first spiral blade 10 e and a second spiral blade 10 f providedon the outer circumferential surface of the rotation shaft 10 d.

On the other hand, the recording material 21 to which the toner imagehas been transferred is nipped and conveyed by a fixing roller and apressure roller provided in a fixing device serving as a fixing portion(not illustrated). In the process, the toner image is heated andpressurized to be heat-fused and heat-fixed on the recording material 21and then discharged onto a discharge tray (not illustrated).

<Process Cartridge>

In the image forming apparatus 7 illustrated in FIG. 1, thephotosensitive drum 1, the charging roller 3, and the cleaning member 4which rotates in the direction of the arrow E in FIG. 1 to clean thesurface of the charging roller 3 are rotatably supported in a unit case.Furthermore, the base end of the cleaning blade 2 is fixedly supportedby the unit case. These elements are integrally provided to include aprocess cartridge. The process cartridge is mounted to be detachablyattachable to the main body of the image forming apparatus 7.

<Recovered Material>

In general, the developer (toner) which becomes a recovered material isa magnetic resin particle. The base material of the magnetic resinparticle is mainly configured with a binder resin and contains a chargecontrol agent and magnetic powder. An external additive blended for thepurpose of improving performance such as charging stability, lubricityimparting, abrasive property imparting, and scattering prevention isattached around a base material thereof.

In this embodiment, the external addition amount of strontium titanateexternally added as abrasive particles for polishing the surface of thephotosensitive drum 1 is preferably in a range of 0.1 parts by weight to25 parts by weight with respect to 100 parts by weight of the tonerparticles. More preferably, the external addition amount of strontiumtitanate is preferably in a range of 2.0 parts by weight to 3.0 parts byweight with respect to 100 parts by weight of the toner particles.

If the external addition amount of strontium titanate is less than 0.1parts by weight with respect to 100 parts by weight of the tonerparticles, the polishing effect cannot be sufficiently exhibited. Inaddition, if the external addition amount of strontium titanate exceeds25 parts by weight with respect to 100 parts by weight of the tonerparticles, cohesiveness is increased. As a result, there are problems inthat the developability is reduced and, due to the strong polishingeffect, the photosensitive member on the surface of the photosensitivedrum 1 is excessively scraped or scratched.

As the abrasive according to this embodiment, strontium titanate wasused. As other similar abrasives, there may be applied oxides such as asilicon oxide, an aluminum oxide, a titanium oxide, a zinc oxide, azirconium oxide, a chromium oxide, a cerium oxide, a tungsten oxide, anantimony oxide, a copper oxide, a tin oxide, a tellurium oxide, amanganese oxide, a boron oxide, and the like. Furthermore, there may beapplied oxides such as a barium titanate, an aluminum titanate, amagnesium titanate, and a calcium titanate, carbides such as a siliconcarbide, a tungsten carbide, a boron carbide, and a titanium carbide,and nitrides such as a silicon nitride, a titanium nitride and a boronnitride. Furthermore, other organic particles or the like may also beused.

The abrasive added to the toner is preferably cubic particles, whichhave a high polishing effect. The cubic particles have an averageparticle size of 30 nm to 300 nm and, more preferably, an averageparticle size of 40 nm to 250 nm. If the average particle size is lessthan 30 nm, the polishing effect of the particles in the cleaner portionis insufficient. On the other hand, if the average particle size exceeds300 nm, the polishing effect is too strong, so that the photosensitivemember on the surface of the photosensitive drum 1 is scratched, whichis not suitable. In the remaining toner conveying apparatus 14 accordingto this embodiment, besides the magnetic remaining toner containingexternal additives such as the above-described abrasives, the entirepowder particles may be set as recovering objects.

<Remaining Toner Conveying Apparatus>

Next, a configuration of the remaining toner conveying apparatus 14 willbe described with reference to FIGS. 2 to 6. FIG. 2 is an explanatorycross-sectional diagram illustrating the configuration of the remainingtoner conveying apparatus 14 according to this embodiment. FIG. 3 is anexplanatory perspective diagram illustrating the configuration of theremaining toner conveying apparatus 14 according to this embodiment.FIG. 4 is a cross-sectional view taken along line G-G in FIG. 2 and isan explanatory diagram illustrating a state of the remaining toner 8 bin the image forming region R1 in the conveyance path 11 according tothis embodiment. FIG. 5 is a cross-sectional view taken along line H-Hin FIG. 2 and is an explanatory diagram illustrating a state in whichthe remaining toner 8 b in the vicinity of the discharge outlet 11 c ofthe discharge portion 11 b in the downstream side in the conveyancedirection of the remaining toner 8 b of the image forming region R1 inthe conveyance path 11 according to this embodiment. FIG. 6 is anexplanatory front diagram illustrating the configuration of theconveying screw 10 according to this embodiment.

As illustrated in FIG. 4, the transfer residual toner 8 a remaining onthe surface of the photosensitive drum 1 after the transfer is scrapedoff by the cleaning blade 2 serving as a cleaning portion with therotation of the photosensitive drum 1 in the direction of the arrow A inFIG. 4. Furthermore, the transfer residual toner is scooped up by ascooping sheet 13 provided to face the cleaning blade 2 to be recoveredas the remaining toner 8 b (toner) from the opening 11 a of theconveyance path 11 into the conveyance path 11.

As illustrated in FIGS. 2 and 3, the conveyance path 11 is providedalong the longitudinal direction of the photosensitive drum 1 to conveythe remaining toner 8 b (toner) scraped off and recovered by thecleaning blade 2 (cleaning portion). The conveying screw 10 serving as aconveying member is provided inside the conveyance path 11 (in theconveyance path) so as to be rotatable around the rotation shaft 10 d inthe direction of the arrow C in FIG. 4. The rotation shaft 10 d of theconveying screw 10 is rotatably supported by bearings 11 d and 11 eprovided on the wall surfaces of the conveyance path 11.

The conveying screw 10 provided inside the conveyance path 11 rotates inthe direction of the arrow C in FIG. 4. As a result, the remaining toner8 b recovered into the conveyance path 11 is conveyed in the directionof the arrow X in FIG. 2 and discharged and stored into a recovery box(not illustrated) from the discharge outlet 11 c of the dischargeportion 11 b provided at the longitudinal end (left side in FIGS. 2 and3) of the conveyance path 11.

As illustrated in FIG. 2, a gear 15 is fixed to one end of the rotationshaft 10 d of the conveying screw 10, and the gear 15 is engaged with adriving gear 17 which is rotation-driven by a motor 16 serving as adriving source. The motor 16 is driven and controlled by a centralprocessing unit (CPU) 18 serving as a controller.

A read only memory (ROM) 19 serving as a storage portion is connected tothe CPU 18. The ROM 19 stores a program or the like corresponding to apredetermined control procedure. The CPU 18 reads the program andcontrols each component of the image forming apparatus 7.

Furthermore, a random access memory (RAM) 20 serving as a storageportion in which working data and input data are stored is alsoconnected to the CPU 18. The CPU 18 controls the image forming apparatus7 with reference to the data stored in the RAM 20 based on theabove-described program and the like.

<Conveying Member>

Next, a configuration of the conveying screw 10 serving as a conveyingmember will be described with reference to FIG. 6. As illustrated inFIG. 6, the conveying screw 10 is configured to have a first spiralblade 10 e provided on the image forming region R1 on the surface of thephotosensitive drum 1 on the outer circumferential surface of therotation shaft 10 d.

Furthermore, the conveying screw 10 has a second spiral blade 10 fprovided in a region R2 in the vicinity of the discharge outlet 11 c ofthe discharge portion 11 b of the conveyance path 11 in the downstreamside of the first spiral blade 10 e in the conveyance direction of theremaining toner 8 b (downstream in the toner conveyance direction)indicated by the direction of the arrow X in FIG. 2. Herein, the imageforming region R1 on the surface of the photosensitive drum 1 denotes aregion on the surface of the photosensitive drum 1 which the recordingmaterial 21 having a maximum width used for the image forming apparatus7 is in contact with.

The conveying force of the remaining toner 8 b conveyed by the firstspiral blade 10 e of the conveying screw 10 is set to be smaller thanthe conveying force of the remaining toner 8 b conveyed by the secondspiral blade 10 f. The first spiral blade 10 e of the conveying screw 10is provided in the image forming region R1 on the surface of thephotosensitive drum 1. The second spiral blade 10 f of the conveyancepath 11 is provided in the region R2 in the vicinity of the dischargeoutlet 11 c of the discharge portion 11 b. In this embodiment, asillustrated in FIGS. 2 and 6, the outer diameter D1 of the first spiralblade 10 e is set to be smaller than the outer diameter D2 of the secondspiral blade 10 f.

In addition, the conveying force referred to in the embodiment refers toan amount of remaining toner to be conveyed in a predetermined time.

As illustrated in FIGS. 2 and 3, the transfer residual toner 8 aremaining on the surface of the photosensitive drum 1 after the transferof the toner image formed on the surface of the photosensitive drum 1 tothe recording material 21 is scraped off by the cleaning blade 2illustrated in FIG. 4 with the rotation of the photosensitive drum 1 inthe arrow A direction. The transfer residual toner 8 a scraped off bythe cleaning blade 2 is recovered as a remaining toner 8 b from theopening 11 a of the conveyance path 11 formed between the distal end ofthe cleaning blade 2 and the distal end of the scooping sheet 13 intothe conveyance path 11. At this time, the remaining toner 8 b convectsin the direction of the arrow F in FIG. 4 in the space formed betweenthe opening 11 a and the outer circumferential end of the first spiralblade 10 e due to the rotational force of the photosensitive drum 1 inthe direction of the arrow A illustrated in FIG. 4.

The remaining toner 8 b convecting in the direction of the arrow F inFIG. 4 comes into contact with the surface of the photosensitive drum 1again. The remaining toner 8 b contains an abrasive in advance, and theabrasive convects in the direction of the arrow F in FIG. 4 to polishthe surface of the photosensitive drum 1. The conveying screw 10(conveying portion) sets the conveying speed of the image forming regionR1 (first region) illustrated in FIG. 2 to be a speed for convecting theremaining toner 8 b (toner) recovered by the cleaning blade (introducingportion) to polish the surface of the photosensitive drum 1 (imagebearing member). After that, the remaining toner 8 b (toner) convects inthe direction of the arrow F in FIG. 4 to reaches the first spiral blade10 e again and is conveyed in the conveyance path 11 in the direction ofthe arrow X in FIG. 2 by the first spiral blade 10 e.

The remaining toner 8 b is conveyed in the conveyance path 11 in thedirection of the arrow X in FIG. 2 by the first spiral blade 10 e.Furthermore, the remaining toner 8 b is conveyed to the discharge outlet11 c of the discharge portion 11 b by the second spiral blade 10 fprovided in the region R2 in the vicinity of the discharge outlet 11 cof the discharge portion 11 b of the conveyance path 11 in thedownstream side of the image forming region R1. After that, theremaining toner 8 b is discharged from the discharge outlet 11 c into arecovery box (not illustrated).

In the conveying screw 10 illustrated in FIG. 6, the conveying force ofthe remaining toner 8 b is regulated by the outer diameters D1 and D2 ofthe first and second spiral blades 10 e and 10 f. In addition, theconveying force of the remaining toner 8 b is regulated by theseparation pitches P1 and P2 of the first and second spiral blades 10 eand 10 f along the common rotation shaft 10 d. In addition, theconveying force of the remaining toner 8 b is regulated by theinclination angles θ1 and θ2 of the first and second spiral blades 10 eand 10 f with respect to the plane “a” perpendicular to the rotationshaft 10 d.

Namely, the outer diameters D1 and D2 of the first and second spiralblades 10 e and 10 f of the conveying screw 10 illustrated in FIG. 6 areincreased. Therefore, the conveying cross-sectional area of theremaining toner 8 b conveyed by the spiral blades 10 e and 10 f in thedirection perpendicular to the rotation shaft 10 d of the conveyingscrew 10 can be increased, and circumferential velocities of the firstand second spiral blades 10 e and 10 f becomes faster. As a result, theconveying speed and the conveyance amount of the remaining toner 8 b inthe direction of the rotation shaft 10 d are increased. As a result, theconveying force of the remaining toner 8 b can be set to be large. Inaddition, the amount of remaining toner to be conveyed is an amount ofdeveloper actually transported, as described above. Therefore, theamount varies depending on, for example, an opening area of a conveyancepath (pipe or the like).

In addition, the separation pitches P1 and P2 of the first and secondspiral blades 10 e and 10 f of the conveying screw 10 illustrated inFIG. 6 are increased. Therefore, the conveying distance of the remainingtoner 8 b conveyed by one rotation of the spiral blades 10 e and 10 f ofthe conveying screw 10 in the direction of the rotation shaft 10 d canbe increased. As a result, the conveying force of the remaining toner 8b can be set to be large.

In addition, the inclination angles 91 and 92 of the first and secondspiral blades 10 e and 10 f of the conveying screw 10 with respect tothe plane “a” perpendicular to the rotation shaft 10 d illustrated inFIG. 6 are increased. Therefore, the conveying speed of the remainingtoner 8 b conveyed by one rotation of the spiral blades 10 e and 10 f ofthe conveying screw 10 in the direction of the rotation shaft 10 d canbe increased. As a result, the conveying force of the remaining toner 8b can be set to be large.

For example, the outer diameters D1 and D2 of the first and secondspiral blades 10 e and 10 f become small. Alternatively, the separationpitches P1 and P2 of the first and second spiral blades 10 e and 10 fbecome small. Alternatively, the inclination angles θ1 and θ2 of thefirst and second spiral blades 10 e and 10 f become small. Then, theconveying force of the remaining toner 8 b by the conveying screw 10becomes small, and thus, the remaining toner 8 b stays in the conveyancepath 11.

Namely, the conveying screw 10 (conveying portion) conveys the remainingtoner 8 b (toner) recovered by the cleaning blade 2 (introducingportion) as follows. The remaining toner 8 b (toner) is conveyed to thedischarge portion 11 b discharging the remaining toner 8 b (toner) sothat the conveying speed in the downstream side of the conveyancedirection (left side in FIG. 2) becomes faster than the conveying speedin the upstream side of the conveyance direction (right side in FIG. 2).

In the conveying screw 10 (conveying portion), in the image formingregion R1 (first region) illustrated in FIG. 2 facing the region wherethe toner image of the photosensitive drum 1 (image bearing member) inthe cleaning blade 2 (introducing portion) is formed, the conveyingspeed is set as follows. The conveying speed is set to be slower thanthe conveying speed of the region R2 (second region) in the vicinity ofthe discharge outlet 11 c of the discharge portion 11 b of theconveyance path 11 which does not face the region where the toner imageof the photosensitive drum 1 (image bearing member) in the downstreamside (left side in FIG. 2) of the conveyance direction of the imageforming region R1 (first region) is formed.

As a result, the conveying screw 10 (conveying portion) conveys theremaining toner 8 b (developer) so that the conveyance amount perpredetermined time in the first conveyance path conveying the remainingtoner 8 b (developer) recovered by the cleaning blade 2 (introducingportion) to the discharge portion 11 b is equal to or less than theconveyance amount in the second conveyance path in the downstream sideof the conveyance direction where the conveyance path is narrower thanthe first conveyance path.

As illustrated in FIG. 4, the transfer residual toner 8 a remaining onthe surface of the photosensitive drum 1 is applied with a force in therotational direction of the photosensitive drum 1 indicated by thedirection of the arrow A in FIG. 4. Then, the transfer residual toner isscraped off by the cleaning blade 2. Then, the remaining toner 8 b isapplied with the force in the rotational direction of the photosensitivedrum 1 and, thus, the remaining toner has a force of rotating andconvecting in the direction of the arrow F in FIG. 4 in the space formedbetween the opening 11 a and the outer circumferential end of the firstspiral blade 10 e in the conveyance path 11.

By the applied rotational force of the photosensitive drum 1, theremaining toner 8 b applied with the rotational force of the directionof the arrow F in FIG. 4 comes in contact with the surface of thephotosensitive drum 1 through the opening 11 a of the conveyance path 11again and, thus, the surface of the photosensitive drum 1 is polished bythe abrasive contained in the remaining toner 8 b. The remaining toner 8b applied with the rotational force to convect in the conveyance path 11in the direction of the arrow F in FIG. 4 is also applied with a forceallowing the remaining toner to convect in the conveyance path 11 in thedirection opposite to the direction of the arrow F in FIG. 4 by thefirst spiral blade 10 e rotating in the direction of the arrow C in FIG.4.

In the region R2 in the vicinity of the discharge outlet 11 c of thedischarge portion 11 b of the conveyance path 11, the dischargeabilityfor discharging the remaining toner 8 b to the discharge outlet 11 c isprioritized over the polishing effect of the surface of thephotosensitive drum 1 by the remaining toner 8 b. For this reason,preferably, various conditions of the second spiral blade 10 f are setso that the force of convecting the remaining toner 8 b in theconveyance path 11 in the direction opposite to the direction of thearrow F in FIG. 5 is increased by the second spiral blade 10 f rotatingin the direction of the arrow C in FIG. 5.

The transfer residual toner 8 a remaining on the surface of thephotosensitive drum 1 is scraped off by the cleaning blade 2. Afterthat, the transfer residual toner is applied with the rotational forceof the direction of the arrow A of the photosensitive drum 1 to berecovered while convecting in the direction of the arrow F in FIG. 4from the opening 11 a in the conveyance path 11. The remaining toner 8 bpolishes the surface of the photosensitive drum 1 and then reaches thefirst spiral blade 10 e. Then, the remaining toner is conveyed in theconveyance path 11 to the discharge portion 11 b by the first spiralblade 10 e. After that, the remaining toner is conveyed in the dischargeportion 11 b by the second spiral blade 10 f to be discharged from thedischarge outlet 11 c into a recovery box (not illustrated).

The outer diameter D2 of the second spiral blade 10 f provided in theregion R2 in the vicinity of the discharge outlet 11 c of the dischargeportion 11 b of the conveyance path 11 of the conveying screw 10illustrated in FIG. 6 is set to be large. Then, the second distance L2between the wall surface of the discharge portion 11 b of the conveyancepath 11 and the outer circumferential end of the second spiral blade 10f illustrated in FIG. 5 is set to be small. As a result, the conveyingforce of the remaining toner 8 b by the second spiral blade 10 frotating in the direction of the arrow C in FIG. 5 can be increased.

In this embodiment, the second distance L2 between the opening 11 a ofthe conveyance path 11 facing the surface of the photosensitive drum 1and the outer circumferential end of the second spiral blade 10 fillustrated in FIG. 5 is set to be in a range of 0.8 times or more andless than 1.3 times the radius r2 (=D2/2) of the second spiral blade 10f.

The second distance L2 between the opening 11 a of the conveyance path11 and the outer circumferential end of the second spiral blade 10 fillustrated in FIG. 5 is set to be such a numerical value that thesecond spiral blade 10 f does not interfere with peripheral members suchas the inner wall surface of the conveyance path 11, the cleaning blade2, and the scooping sheet 13. In addition, the upper limit of the seconddistance L2 is appropriately set so that, due to the lowering of theconveying force of the remaining toner 8 b by the second spiral blade 10f, the remaining toner 8 b is not clogged in the region R2 in thevicinity of the discharge outlet 11 c of the discharge portion 11 b ofthe conveyance path 11, and thus, the conveying screw 10 is not broken.

In this embodiment, the outer diameter D2 of the second spiral blade 10f provided in the region R2 in the vicinity of the discharge outlet 11 cof the discharge portion 11 b of the conveyance path 11 is 14 mm, andthe outer diameter D3 of the rotation shaft 10 d is 5 mm. The seconddistance L2 between the opening 11 a of the conveyance path 11 and theouter circumferential end of the second spiral blade 10 f is set to be6.05 mm. In this embodiment, the separation pitches P1 and P2 of thefirst and second spiral blades 10 e and 10 f of the conveying screw 10along the rotation shaft 10 d are set to be equally 10 mm.

As illustrated in FIG. 4, in this embodiment, clearances between theouter circumferential end of the first spiral blade 10 e and inner wallsurfaces of the conveyance path 11 in the image forming region R1 of theconveying screw 10 in the conveyance path 11 are as follows. A distanceL11 from the center of the rotation shaft 10 d to the upper wall surfaceof the conveyance path 11 is 9.04 mm. In addition, a distance L12 fromthe center of the rotation shaft 10 d to the wall surface of theconveyance path 11 in the upstream side of the rotational direction ofthe photosensitive drum 1 in the direction of the arrow A in FIG. 4 is8.01 mm.

A distance L13 from the center of the rotation shaft 10 d to the wallsurface of the conveyance path in the downstream side of the rotationaldirection of the photosensitive drum 1 is 10.98 mm. A distance L14 fromthe center of the rotation shaft 10 d to the opening 11 a of theconveyance path 11 is 13.05 mm. In addition, a distance L15 from thecenter of the rotation shaft 10 d to the inner surface of the cleaningblade 2 is set to be 12.16 mm.

<Effect of Suppressing Image Flow>

The effect of suppressing the image flow in this embodiment wasconfirmed by using the image forming apparatus 7 which is an A3-sizemulti-function printer (MFP) of which the maximum size of the recordingmaterial 21 is A3 size. As the charging roller 3, an elastic solidroller having a three-layered structure of a base layer made of anelastic layer, a dielectric layer, and a protective layer is used.

The outer diameter of the charging roller 3 is 16 mm, and the Asker Chardness is 48±5°. The outer diameter of the photosensitive drum 1 is 30mm, and the rotational speed (circumferential velocity) is 230 mm/sec.The photosensitive drum 1 is driven to be rotated by a motor 22 servingas a drive source. The driving of the motor 22 is controlled by a CPU 18which is a controller. The number of rotations of the conveying screw 10driven to be rotated by the motor 16 of which driving is controlled bythe CPU 18 in one minute is set to be 234.3 rpm (rotation per minute).

The outer diameter D2 of the second spiral blade 10 f provided in theregion R2 in the vicinity of the discharge outlet 11 c of the dischargeportion 11 b of the conveyance path 11 of the conveying screw 10according to this embodiment is 14 mm. The rotational speed(circumferential velocity) V2 (mm/sec) of the second spiral blade 10 fis expressed by the following Mathematical Formula 1. Herein, ω(rad/sec) is the angular velocity (angle per second) of the conveyingscrew 10. When the conveying screw 10 is rotated once, the angle is 360degrees, that is, 2π (rad). The radius of the second spiral blade 10 fis r2 (=D2/2).

[Mathematical Formula 1]

V2=Ω×r2

V2=234.3 (rpm)×2π/60 (sec)×7(mm)

V2≈171.75 (mm/sec)

Therefore, the rotational speed (circumferential velocity) V2 of thesecond spiral blade 10 f provided in the region R2 in the vicinity ofthe discharge outlet 11 c of the discharge portion 11 b of theconveyance path 11 of the conveying screw 10 is approximately 172(mm/sec). The rotational speed (circumferential velocity) of thephotosensitive drum 1 is 230 (mm/sec). As a result, the rotational speed(circumferential velocity) V2 of the second spiral blade 10 f is about0.75 times (172 (mm/sec)/230 (mm/sec)≈0.747) the rotational speed(circumferential velocity) of the photosensitive drum 1.

<Comparative Example>

As Comparative Example, the outer diameter D1 of the first spiral blade10 e provided in the image forming region R1 of the conveying screw 10illustrated in FIG. 2 is equal to the outer diameter D2 of the secondspiral blade 10 f provided in the region R2 in the vicinity of thedischarge outlet 11 c of the discharge portion 11 b of the conveyancepath 11 and is set to be 14 mm.

As illustrated in FIG. 5, the transfer residual toner 8 a remaining onthe surface of the photosensitive drum 1 after the transfer is scrapedoff by the cleaning blade 2. In Comparative Example, it is known thatthe transfer residual toner is applied with a force of the rotationaldirection of the photosensitive drum 1 and, thus, the convectionperformance is deteriorated in the convection in the direction of thearrow F in FIG. 4 in the conveyance path 11 from the opening 11 a.

As illustrated in FIG. 4, the transfer residual toner 8 a remaining onthe surface of the photosensitive drum 1 after the transfer is scrapedoff by the cleaning blade 2. Then, the remaining toner 8 b is appliedwith the force in the rotational direction of the photosensitive drum 1indicated by the direction of the arrow A in FIG. 4 and is recoveredinto the conveyance path 11 from the opening 11 a and, thus, theremaining toner has a force of convecting in the direction of the arrowF in FIG. 4. By this force, the remaining toner 8 b comes into contactwith the surface of the photosensitive drum 1 again from the opening 11a of the conveyance path 11, and the surface of the photosensitive drum1 is polished by the abrasive contained in the remaining toner 8 b. Theremaining toner 8 b applied with the force convecting in the directionof the arrow F in FIG. 4 in the conveyance path 11 is also applied witha force in the opposite direction due to the conveying screw 10 rotatingin the direction of the arrow C in FIG. 4.

It is preferable that, in the image forming region R1 illustrated inFIG. 2, the polishing effect of the surface of the photosensitive drum 1is improved. Therefore, the occurrence of image flow caused by electricdischarge products adhering to the surface of the photosensitive drum 1can be suppressed. In addition, it is also necessary to suppress theoccurrence of a phenomenon called paper dust net where the paper dustcoming from the recording material 21 stays in the vicinity of theopening 11 a of the conveyance path 11.

In order to suppress the occurrence of image flow and paper dust net,preferably, the conditions of the conveying screw 10 are set so that theforce of convecting the remaining toner 8 b in the conveyance path 11 inthe direction of the arrow F in FIG. 4 is not hindered. In some cases,The force of convecting the remaining toner 8 b in the conveyance path11 in the direction of the arrow F in FIG. 4 is hindered by the force ofconvecting the remaining toner 8 b in the conveyance path 11 in thedirection of the arrow C in FIG. 4 according to the rotation of theconveying screw 10 in the direction of the arrow C in FIG. 4.

In order to suppress the occurrence of image flow and paper dust net,the outer diameter D1 of the first spiral blade 10 e provided in theimage forming region R1 of the conveying screw 10 illustrated in FIG. 6is set to be small. In addition, the first distance L1 between theopening 11 a of the conveyance path 11 and the outer circumferential endof the first spiral blade 10 e illustrated in FIG. 4 is set to be large.As a result, the force of convecting the remaining toner 8 b in theconveyance path 11 in the direction of the arrow C in FIG. 4 accordingto the rotation of the conveying screw 10 in the direction of the arrowC in FIG. 4 can be decreased. Then, the force of convecting theremaining toner 8 b in the conveyance path 11 in the direction of thearrow F in FIG. 4 according to the rotation of the photosensitive drum 1in the direction of the arrow A in FIG. 4 can be increased.

In this embodiment, the outer diameter D1 of the first spiral blade 10 eprovided in the image forming region R1 of the conveying screw 10illustrated in FIG. 6 is set to be 10 mm, and the outer diameter D3 ofthe rotation shaft 10 d is set to be 5 mm. In addition, as illustratedin FIG. 4, the first distance L1 between the opening 11 a of theconveyance path 11 and the outer circumferential end of the first spiralblade 10 e provided in the image forming region R1 is set to be 8.05 mm.

The outer diameter D1 of the first spiral blade 10 e provided in theimage forming region R1 of the conveying screw 10 according to thisembodiment is 10 mm. Similarly to Mathematical Formula 1, the rotationalspeed (circumferential velocity) V1 (mm/sec) of the first spiral blade10 e provided in the image forming region R1 is expressed by thefollowing Mathematical Formula 2. Herein, ω (rad/sec) is the angularvelocity (angle per second) of the conveying screw 10. When theconveying screw 10 is rotated once, the angle is 360 degrees, that is,2π (rad). The radius of the first spiral blade 10 e is denoted by r1(=D1/2).

[Mathematical Formula 2]

V1=ω×r1

V1=234.3(rpm)×2π/60(sec)×5 (mm)

V1≈122.67(mm/sec)

Therefore, the rotational speed (circumferential velocity) V1 of thefirst spiral blade 10 e provided in the image forming region R1 of theconveying screw 10 is approximately 123 (mm/sec). The rotational speed(circumferential velocity) of the photosensitive drum 1 is 230 (mm/sec).As a result, the rotational speed (circumferential velocity) V1 of thefirst spiral blade 10 e provided in the image forming region R1 of theconveying screw 10 is about 0.53 times (123 (mm/sec)/230 (mm/sec)≈0.534)the rotational speed (circumferential velocity) of the photosensitivedrum 1.

As a result, the force of convecting the remaining toner 8 b in theconveyance path 11 in the direction of the arrow C in FIG. 4 accordingto the rotation of the conveying screw 10 in the direction of the arrowC in FIG. 4 can be decreased. Then, the force of convecting theremaining toner 8 b in the conveyance path 11 in the direction of thearrow F in FIG. 4 according to the rotation of the photosensitive drum 1in the direction of the arrow A in FIG. 4 can be increased.

As a result, the remaining toner 8 b comes into contact with the surfaceof the photosensitive drum 1 again from the opening 11 a of theconveyance path 11, and thus, the surface of the photosensitive drum 1is polished by the abrasive contained in the remaining toner 8 b.Therefore, in the image forming region R1 illustrated in FIG. 2, thepolishing effect on the surface of the photosensitive drum 1 can beimproved. As a result, the surface of the photosensitive drum 1 ispolished by the abrasive contained in the remaining toner 8 b, and thus,the occurrence of image defects called image flow caused by electricdischarge products attached by the electric discharge phenomenon of thecharging roller 3 can be suppressed.

The convection performance of the remaining toner 8 b in the imageforming region R1 in the conveyance path 11 in the direction of thearrow F in FIG. 4 according to the rotation of the photosensitive drum 1in the direction of the arrow A in FIG. 4 is set so as not to beobstruct by the rotation of the conveying screw 10 in the direction ofthe arrow C in FIG. 4. Therefore, the rotational speed (circumferentialvelocity) V1 of the first spiral blade 10 e provided in the imageforming region R1 of the conveying screw 10 is set to be in a range ofat least 0.4 times or more and less than 0.6 times the rotational speed(circumferential velocity) of the photosensitive drum 1.

More preferably, the rotational speed (circumferential velocity) V1 ofthe first spiral blade 10 e is set to be in a range of 0.5 times or moreand less than 0.6 times the rotational speed (circumferential velocity)of the photosensitive drum 1. The outer diameter D1 of the first spiralblade 10 e provided in the image forming region R1 of the conveyingscrew 10 is appropriately set so that the rotational speed(circumferential velocity) V1 of the first spiral blade 10 e is obtainedas described above.

In this embodiment, preferably, the outer diameter D1 of the firstspiral blade 10 e provided in the image forming region R1 of theconveying screw 10 is set to be in a range of 8 mm or more and less than11 mm. More preferably, the outer diameter D1 of the first spiral blade10 e provided in the image forming region R1 of the conveying screw 10is set to be in a range of 10 mm or more and less than 11 mm.

The lower limit value of the ratio between the rotational speed(circumferential velocity) V1 of the first spiral blade 10 e provided inthe image forming region R1 of the conveying screw 10 and the rotationalspeed (circumferential velocity) of the photosensitive drum 1 is set asfollows. The lower limit value is determined from the dischargeabilityof the remaining toner 8 b conveyed in the direction of the arrow X inFIG. 2 by the conveying screw 10 in the conveyance path 11. In addition,the upper limit value of the ratio between the rotational speed(circumferential velocity) V1 of the first spiral blade 10 e and therotational speed (circumferential velocity) of the photosensitive drum 1is set as follows. The upper limit value of the ratio is determined bythe convection performance of the remaining toner 8 b in the imageforming region R1 in the conveyance path 11 in the direction of thearrow F in FIG. 4 according to the rotation of the photosensitive drum 1in the direction of the arrow A in FIG. 4.

Namely, the first distance L1 between the opening 11 a facing thesurface of the photosensitive drum 1 of the conveyance path 11 and theouter circumferential end of the first spiral blade 10 e illustrated inFIG. 4 is set as follows. Preferably, the first distance L1 is set to bein a range of 1.3 times or more and less than 2.5 times the radius r1(=D1/2) of the outer diameter D1 of the first spiral blade 10 e providedin the image forming region R1 of the conveying screw 10.

More preferably, the first distance L1 between the opening 11 a of theconveyance path 11 and the outer circumferential end of the first spiralblade 10 e is set to be larger than 1.35 times or more and less than 2.0times the radius r1 of the first spiral blade 10 e provided in the imageforming region R1.

In a case where the outer diameter D1 of the first spiral blade 10 eprovided in the image forming region R1 of the conveying screw 10 ischanged from 14 mm in Comparative Example to 10 mm, a blur state ofcharacters caused by the image flow is improved by about 15% to 20% incomparison with Comparative Example. The blur state of the characters isperformed by comparing the number of black pixels when a binary processof the character image is performed.

<Comparison of Conveying Force of Remaining Toner>

FIG. 7 illustrates a result of comparison of the conveying forces of theremaining toner 8 b according to difference in the outer diameters D1and D2 of the spiral blades 10 e and 10 f of the conveying screw 10. Thegraph “b” in FIG. 7 illustrates the conveying force of the remainingtoner 8 b by the remaining toner conveying apparatus 14 according toComparative Example in which the outer diameter D1 of the first spiralblade 10 e provided in the image forming region R1 of the conveyingscrew 10 is set to be 14 mm.

The graph “d” in FIG. 7 illustrates the conveying force of the remainingtoner 8 b by the remaining toner conveying apparatus 14 according tothis embodiment in which the outer diameter D1 of the first spiral blade10 e provided in the image forming region R1 of the conveying screw 10is set to be 10 mm. The conveying force of the remaining toner 8 bconveyed in the conveyance path 11 is indicated by the discharge amountof the remaining toner 8 b discharged from the discharge outlet 11 c ofthe discharge portion 11 b of the conveyance path 11.

It can be seen that the conveying force according to this embodiment(D1=10 mm) illustrated by graph “d” in FIG. 7 is decreased by 10% onaverage and 20% in maximum in comparison with the conveying force ofComparative Example (D1=14 mm) illustrated by graph “b” in FIG. 7.Herein, the conveying force of the remaining toner 8 b is as follows.The amount of toner accumulated in the conveyance path 11 in a casewhere a certain amount of toner is fed into the conveyance path 11 inthe absence of the conveying screw 10 in the conveyance path 11 is setas a reference. The ratio of weight of the remaining toner 8 bdischarged from the discharge outlet 11 c of the discharge portion 11 bof the conveyance path 11 when the conveying screw 10 is provided in theconveyance path 11 is calculated.

In this embodiment, as illustrated in FIG. 4, in the image formingregion R1 of the photosensitive drum 1, the transfer residual toner 8 aremaining on the surface of the photosensitive drum 1 after the transferis scraped off by the cleaning blade 2, and the transfer residual toneris recovered as the remaining toner 8 b from the opening 11 a of theconveyance path 11.

The outer diameter D1 (10 mm) of the first spiral blade 10 e of theconveying screw 10 is smaller than the outer diameter D2 (14 mm) of thesecond spiral blade 10 f. The first spiral blade 10 e is provided in theimage forming region R1. The second spiral blade 10 f of the conveyancepath 11 is provided in the region R2 in the vicinity of the dischargeoutlet 11 c of the discharge portion 11 b.

The first distance L1 (8.05 mm) between the opening 11 a of theconveyance path 11 and the outer circumferential end of the first spiralblade 10 e provided in the image forming region R1 of the conveyingscrew 10 is set as follows. The first distance L1 is set to be largerthan the second distance L2 (6.05 mm) between the opening 11 a and theouter circumferential end of the second spiral blade 10 f.

As a result, as illustrated in FIG. 4, the convection performance of theremaining toner 8 b in the vicinity of the opening 11 a of theconveyance path 11 in the image forming region R1 in the direction ofthe arrow F in FIG. 4 can be secured. As a result, the polishing of thesurface of the photosensitive drum 1 being in contact with the opening11 a of the conveyance path 11 is facilitated by the remaining toner 8 bcontaining the abrasive, and thus, the occurrence of the image flow canbe suppressed. In addition, by securing the convection performance ofthe remaining toner 8 b in the vicinity of the opening 11 a of theconveyance path 11 in the direction of the arrow F in FIG. 4, it ispossible to suppress the paper dust net in which the paper dust comingfrom the recording material 21 stays in the vicinity of the opening 11 aof the conveyance path 11.

In addition, the outer diameter D2 (14 mm) of the second spiral blade 10f provided in the regions other than the image forming region R1,particularly, in the region R2 in the vicinity of the discharge outlet11 c of the discharge portion 11 b of the conveyance path 11 is large.As a result, it is possible to increase the conveyability (amount oftoner that can be conveyed for a predetermined time) of the remainingtoner 8 b conveyed in the discharge portion 11 b of the conveyance path11. As a result, the remaining toner 8 b is not clogged in the vicinityof the discharge outlet 11 c of the discharge portion lib, and thus, itis possible to prevent the conveying screw 10 from being broken.

In addition, if the conveyability of the remaining toner 8 b in theregion R2 in the vicinity of the discharge outlet is equal to or greaterthan the conveyability in the image forming region R1, clogging of theremaining toner 8 b in the vicinity of the discharge outlet 11 c anddamage of the conveying screw 10 can be prevented.

As a result, the convection performance of the remaining toner 8 b inthe direction of the arrow F in FIG. 4 in the space formed between thesurface of the photosensitive drum 1 and the outer circumferential endof the first spiral blade 10 e provided in the image forming region R1through the opening 11 a of the conveyance path 11 can be improved. As aresult, the polishing of the surface of the photosensitive drum 1 beingin contact with the opening 11 a of the conveyance path 11 isfacilitated by the remaining toner 8 b containing the abrasive, andthus, the occurrence of the image flow can be suppressed. In addition,the occurrence of paper dust net can also be suppressed. Furthermore,the dischargeability of the remaining toner 8 b in the region R2 in thevicinity of the discharge outlet 11 c of the discharge portion 11 b ofthe conveyance path 11 can be maintained, and thus, clogging of theremaining toner 8 b in the discharge portion 11 b of the conveyance path11 can be prevented.

In the embodiment, a conveyance amount of the remaining toner (residualtoner) in a predetermined time is set as the conveying force, and theconveying force in the image forming region R1 and the conveying forcein the vicinity region R2 have been described.

However, with respect to the conveying capability of a spiral bladedefined by a pitch, angle, and outer diameter of the blade, theconveying capability in the vicinity region R2 may exceed the conveyingcapability in the image forming region R1.

This also applies to the following embodiments.

Second Embodiment

Next, a configuration of a second embodiment of the image formingapparatus provided with the remaining toner conveying apparatusaccording to the invention will be described with reference to FIGS. 8and 9. The components configured in the same manner as in the firstembodiment are denoted by the same reference numerals or by the samenames with different reference numerals, and the description thereof isomitted. FIG. 8 is an explanatory front diagram illustrating theconfiguration of the conveying screw according to this embodiment. FIG.9 is a diagram illustrating a result of comparison of the conveyingforces of the remaining toner according to the difference in theseparation pitches in the rotation shaft direction of the spiral bladesof the conveying screw according to this embodiment.

In the conveying screw 10 according to the first embodiment, asillustrated in FIG. 6, the outer diameter D1 (10 mm) of the first spiralblade 10 e provided in the image forming region R1 is set as follows.The outer diameter D1 is set to be smaller than the outer diameter D2(14 mm) of the second spiral blade 10 f provided in the region R2 in thevicinity of the discharge outlet 11 c of the discharge portion 11 b ofthe conveyance path 11.

Furthermore, a separation pitch P1 of the first spiral blade 10 eprovided in the image forming region R1 along the rotation shaft 10 dand a separation pitch P2 of the second spiral blade 10 f provided inthe region R2 in the vicinity of the discharge outlet 11 c of thedischarge portion 11 b along the rotation shaft 10 d are set to beequally 10 mm. In this embodiment, similarly to the first embodiment, asillustrated in FIG. 8, the outer diameter D1 (10 mm) of the first spiralblade 10 e of the conveying screw 10 is set to be smaller than the outerdiameter D2 (14 mm) of the second spiral blade 10 f.

In this embodiment, furthermore, the separation pitch P2 (20 mm) of thesecond spiral blade 10 f along the rotation shaft 10 d is set to belarger than the separation pitch P1 (10 mm) of the first spiral blade 10e along the rotation shaft 10 d.

Namely, the separation pitch P1 (10 mm) of the first spiral blade 10 ealong the rotation shaft 10 d is set to be smaller than the separationpitch P2 (20 mm) of the second spiral blade 10 f along the rotationshaft 10 d. As a result, in comparison with the first embodiment, theconveying force of the remaining toner 8 b in the region R2 in thevicinity of the discharge outlet 11 c of the discharge portion 11 b ofthe conveyance path 11 can be further increased.

In addition, in this embodiment, the inclination angles θ1 and θ2 of thefirst and second spiral blades 10 e and 10 f of the conveying screw 10with respect to the plane “a” perpendicular to the rotation shaft 10 dillustrated in FIG. 8 are set to be equally to 15°.

In this embodiment, the separation pitch P2 of the second spiral blade10 f of the conveying screw 10 along the rotation shaft 10 d is set tobe large. As a result, it can be seen that the conveying force ofconveying the remaining toner 8 b in the region R2 in the vicinity ofthe discharge outlet 11 c of the discharge portion 11 b of theconveyance path 11 by the second spiral blade 10 f in the direction ofthe arrow X in FIG. 2 is increased.

For example, in the related art, the separation pitch P1 of the firstspiral blade 10 e provided in the image forming region R1 along therotation shaft 10 d is 10 mm. The separation pitch P2 of the secondspiral blade 10 f provided in the region R2 in the vicinity of thedischarge outlet 11 c of the discharge portion 11 b in the conveyancepath 11 along the rotation shaft 10 d is set to be 15 mm which is 1.5times the separation pitch P1 (10 mm).

Then, it can be seen that the conveying force of conveying the remainingtoner 8 b in the direction of the arrow X in FIG. 2 by the second spiralblade 10 f is increased by about 4% to 5% than the conveying force ofconveying the remaining toner 8 b in the direction of the arrow X inFIG. 2 by the first spiral blade 10 e.

It is preferable that the separation pitch P2 of the second spiral blade10 f along the rotation shaft 10 d is set to be 1.1 times or more andless than 2.0 times the separation pitch P1 of the first spiral blade 10e along the rotation shaft 10 d.

Conversely, preferably, the separation pitch P2 of the second spiralblade 10 f along the rotation shaft 10 d is set to be more than 0.5times and 0.9 times or less the first spiral blade 10 e.

In some cases, the separation pitch P2 may be smaller than 1.0 times theseparation pitch P1. In those cases, in the region R2 in the vicinity ofthe discharge outlet 11 c of the discharge portion 11 b in theconveyance path 11, a sufficient conveying force of conveying theremaining toner 8 b in the direction of the arrow X in FIG. 2 by thesecond spiral blade 10 f cannot be obtained. As a result, clogging ofthe remaining toner 8 b occurs in the vicinity of the discharge outlet11 c of the discharge portion 11 b, and thus, there is a problem in thatthe conveying screw 10 may be damaged.

Furthermore, in some cases, the separation pitch P2 may be larger than2.0 times the separation pitch P1. In this case, the second spiral blade10 f idles in the remaining toner 8 b in the region R2 in the vicinityof the discharge outlet 11 c of the discharge portion 11 b in theconveyance path 11. As a result, due to a decrease in conveying force,clogging of the remaining toner 8 b may occur, and thus, the conveyingscrew 10 may be damaged.

In this embodiment, the separation pitch P1 of the first spiral blade 10e provided in the image forming region R1 of the conveying screw 10along the rotation shaft 10 d is set to be 10 mm. The separation pitchP2 of the second spiral blade 10 f along the rotation shaft 10 d isappropriately set to be 1.1 times or more and less than 2.0 times (11 mmor more and less than 20 mm) the separation pitch P1 (10 mm) of thefirst spiral blade 10 e.

FIG. 9 is a diagram illustrating comparison of conveying forces ofconveying the remaining toner 8 b in the direction of the arrow X inFIG. 2 by the second spiral blade 10 f when the separation pitch P2 ofthe second spiral blade 10 f of the conveying screw 10 along therotation shaft 10 d is changed. In the graph “f” illustrated in FIG. 9,similarly to the first embodiment, the separation pitches P1 and P2 ofthe first and second spiral blades 10 e and 10 f of the conveying screw10 along the rotation shaft 10 d are set equally 10 mm. In this case,the conveying force of conveying the remaining toner 8 b in thedirection of the arrow X in FIG. 2 by the second spiral blade 10 f isindicated by the discharge amount of the remaining toner 8 b dischargedfrom the discharge outlet 11 c of the discharge portion 11 b of theconveyance path 11.

In the graph “e” illustrated in FIG. 9, according to this embodiment,the separation pitch P1 of the first spiral blade 10 e provided in theimage forming region R1 of the conveying screw 10 along the rotationshaft 10 d is set to be 10 mm. The separation pitch P2 of the secondspiral blade 10 f provided in the region R2 in the vicinity of thedischarge outlet 11 c of the discharge portion 11 b in the conveyancepath 11 along the rotation shaft 10 d is set to be 20 mm. In this case,the conveying force of conveying the remaining toner 8 b in thedirection of the arrow X in FIG. 2 by the second spiral blade 10 f isindicated by the discharge amount of the remaining toner 8 b dischargedfrom the discharge outlet 11 c of the discharge portion 11 b of theconveyance path 11.

As illustrated in FIG. 9, the graph “e” in which the separation pitch P2of the second spiral blade 10 f is set to be larger than the separationpitch P1 of the first spiral blade 10 e is as follows. It can be seenthat the conveying force of the remaining toner 8 b is increased by 8%on average and 11% in maximum with respect to the graph “f” where theseparation pitch P2 of the second spiral blade 10 f is equal to theseparation pitch P1 of the first spiral blade 10 e. The otherconfigurations are the same as those of the first embodiment, and thesame effects can be obtained.

Third Embodiment

Next, a configuration of a third embodiment of the image formingapparatus provided with the remaining toner conveying apparatusaccording to the invention will be described with reference to FIG. 10.FIG. 10 is an explanatory front diagram illustrating the configurationof the conveying screw 10 according to this embodiment. The componentsconfigured in the same manner as in the first embodiment are denoted bythe same reference numerals or by the same names with differentreference numerals, and the description thereof is omitted. In thesecond embodiment, the inclination angles θ1 and θ2 of the first andsecond spiral blades 10 e and 10 f of the conveying screw 10 withrespect to the plane “a” perpendicular to the rotation shaft 10 dillustrated in FIG. 8 are set to be equally 15°.

In this embodiment, as illustrated in FIG. 10, the second inclinationangle θ2 (20°) of the second spiral blade 10 f provided in the region R2in the vicinity of the discharge outlet 11 c of the discharge portion 11b of the conveyance path 11 with respect to the plane “a” perpendicularto the rotation shaft 10 d is set as follows. The second inclinationangle θ2 is set to be larger than the first inclination angle θ1 (15°)of the first spiral blade 10 e provided in the image forming region R1of the conveying screw 10 with respect to the plane “a” perpendicular tothe rotation shaft 10 d.

Namely, in this embodiment, the first inclination angle θ1 (15°) of thefirst spiral blade 10 e of the conveying screw 10 with respect to theplane “a” perpendicular to the rotation shaft 10 d is set as follows.The first inclination angle θ1 is set to be smaller than the secondinclination angle θ2 (20°) of the second spiral blade 10 f with respectto the plane “a” perpendicular to the rotation shaft 10 d.

If the first and second spiral blades 10 e and 10 f of the conveyingscrew 10 are tilted with respect to the rotation shaft 10 d, theconveyability of the remaining toner 8 b is increased. Therefore, inthis embodiment, the second inclination angle θ2 (20°) of the secondspiral blade 10 f with respect to the plane “a” perpendicular to therotation shaft 10 d is set to be larger than the first inclination angleθ1 (15°) of the first spiral blade 10 e with respect to the plane “a”perpendicular to the rotation shaft 10 d. As a result, clogging of theremaining toner 8 b in the vicinity of the discharge outlet 11 c of thedischarge portion 11 b of the conveyance path 11 can be prevented.

In this embodiment, the second inclination angle θ2 of the second spiralblade 10 f provided in the region R2 in the vicinity of the dischargeoutlet 11 c of the discharge portion 11 b of the conveyance path 11 withrespect to the plane “a” perpendicular to the rotation shaft 10 d is setto be 20°. On the other hand, the first inclination angle θ1 of thefirst spiral blade 10 e provided in the image forming region R1 withrespect to the plane “a” perpendicular to the rotation shaft 10 d is setto be 15°.

As a result, the conveying speed of the remaining toner 8 b in thedirection of the arrow X in FIG. 6 by the first spiral blade 10 e in theimage forming region R1 in the conveyance path 11 can be delayed asfollows. The conveying speed can be delayed to be 10% slower than theconveying speed of the remaining toner 8 b in the direction of the arrowX in FIG. 6 by the second spiral blade 10 f in the region R2 in thevicinity of the discharge outlet 11 c of the discharge portion 11 b ofthe conveyance path 11.

Thus, the convection time of the remaining toner 8 b in the direction ofthe arrow F in FIG. 4 in the space between the surface of thephotosensitive drum 1 and the conveying screw 10 in the conveyance path11 through the opening 11 a of the conveyance path 11 can be increased.As a result, the polishing time for the surface of the photosensitivedrum 1 being in contact with the opening 11 a of the conveyance path 11by the remaining toner 8 b containing the abrasive can be increased.Therefore, the occurrence of image flow can be suppressed, and theoccurrence of paper dust net can be suppressed. Furthermore, it can beseen that, since the dischargeability of the remaining toner 8 b in theregion R2 in the vicinity of the discharge outlet 11 c of the dischargeportion 11 b of the conveyance path 11 can also be maintained, cloggingof the remaining toner 8 b does not occur.

The second inclination angle θ2 of the second spiral blade 10 f providedin the region R2 in the vicinity of the discharge outlet 11 c of thedischarge portion 11 b of the conveyance path 11 with respect to theplane “a” perpendicular to the rotation shaft 10 d is preferablyinclined as follows. The first inclination angle θ1 of the first spiralblade 10 e provided in the image forming region R1 is inclined withrespect to the plane “a” perpendicular to the rotation shaft 10 d. Thesecond inclination angle θ2 is preferably greatly inclined in a range of2° or more and less than 5° with respect to the θ1.

In this embodiment, as illustrated in FIG. 10, the outer diameter D1 (10mm) of the first spiral blade 10 e of the conveying screw 10 and theouter diameter D2 (10 mm) of the second spiral blade 10 f are set to beequal to each other. Other configurations are the same as those of theabove embodiments, and the same effects can be obtained.

In the embodiments described heretofore, the conveying force in theimage forming region R1 and the conveying force in the vicinity regionR2 have been described by setting the conveyance amount of the residualtoner in the predetermined time as the conveying force.

However, as illustrated in FIG. 2, with respect to a conveyingcapability of the conveying portion (screw) defined by a shape such as apitch, angle, outer diameter, and shaft thickness of a spiral blade, itis preferable that the conveying capability of the conveying portion inthe image forming region R1 is set to be smaller than the conveyingcapability of the conveying portion in the vicinity region R2. Herein,unlike the conveyance amount, the conveying capability is a value thatdoes not depend on the opening area of the conveyance path and theamount of the developer. As described above, by setting the conveyingcapability in the region R1 and the conveying capability in the regionR2, the conveying speed of the developer in the region R1 by theconveying portion can be set to be slower, so that it is possible tosufficiently polish the image bearing member with the developer. On theother hand, in the region R2, the conveying of the developer by theconveying portion can be speeded up without clogging the developer.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2016-110786, filed Jun. 2, 2016 which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A remaining toner conveying apparatus comprising: an introducing portion configured to introduce a developer remaining on an image bearing member without being transferred; and a conveying portion configured to convey the developer introduced by the introducing portion toward a discharge portion, the conveying portion conveying the developer so that a conveyance amount of the developer per predetermined time in a first conveyance path is equal to or less than a conveyance amount per the predetermined time of the developer in a second conveyance path which is in a downstream side of the first conveyance path in a direction of the conveying and narrower than the first conveyance path.
 2. The remaining toner conveying apparatus according to claim 1, wherein the conveying portion is configured such that the first conveyance path is provided to face a first region where a toner image of the image bearing member is formed, and the second conveyance path is provided in a downstream side of the first region in the conveyance direction to face a second region where the toner image is not formed.
 3. The remaining toner conveying apparatus according to claim 1, wherein the conveying portion is configured with a spiral blade.
 4. The remaining toner conveying apparatus according to claim 3, wherein an outer diameter of the spiral blade in the first conveyance path is set to be smaller than an outer diameter of the spiral blade in the second conveyance path.
 5. The remaining toner conveying apparatus according to claim 4, wherein a distance between an opening facing the image bearing member and the outer circumferential end of the spiral blade in the first conveyance path is set to be 1.3 times or more and less than 2.5 times a radius of the spiral blade in the first conveyance path, and wherein a distance between the opening facing the image bearing member and the outer circumferential end of the spiral blade in the second conveyance path is set to be 0.8 times or more and less than 1.3 times a radius of the spiral blade in the second conveyance path.
 6. The remaining toner conveying apparatus according to claim 3, wherein a separation pitch of the spiral blade in the first conveyance path along a rotation shaft is set to be smaller than a separation pitch of the spiral blade in the second conveyance path along the rotation shaft.
 7. The remaining toner conveying apparatus according to claim 6, wherein the separation pitch in the first conveyance path is set to be in a range of more than 0.5 times and 0.9 times or less the separation pitch in the second conveyance path.
 8. The remaining toner conveying apparatus according to claim 3, wherein an inclination angle of the spiral blade in the first conveyance path with respect to a plane perpendicular to a rotation shaft is set to be smaller than the inclination angle in the second conveyance path.
 9. The remaining toner conveying apparatus according to claim 8, wherein the inclination angle in the first conveyance path is set to be smaller in a range of 2° or more and less than 5° than the inclination angle in the second conveyance path.
 10. The remaining toner conveying apparatus according to claim 1, wherein the conveying portion is configured such that a conveying speed of the developer in the first conveyance path is a speed for convecting the toner introduced by the introducing portion and polishing the surface of the image bearing member.
 11. An image forming apparatus comprising: the image bearing member; and the remaining toner conveying apparatus according to claim
 1. 12. A remaining toner conveying apparatus comprising: an introducing portion configured to introduce a developer remaining on an image bearing member without being transferred; and a conveying portion configured to convey the developer introduced by the introducing portion toward a discharge portion, the conveying portion conveying the developer so that a conveyance amount of the developer per predetermined time in a first conveyance path is less than a conveyance amount per the predetermined time of the developer in a second conveyance path which is in a downstream side of the first conveyance path in a direction of the conveying.
 13. The remaining toner conveying apparatus according to claim 12, wherein the conveying portion is configured such that the first conveyance path is provided to face a first region where a toner image of the image bearing member is formed, and the second conveyance path is provided in a downstream side of the first region in the conveyance direction to face a second region where the toner image is not formed.
 14. The remaining toner conveying apparatus according to claim 12, wherein the conveying portion is configured with a spiral blade.
 15. The remaining toner conveying apparatus according to claim 14, wherein an outer diameter of the spiral blade in the first conveyance path is set to be smaller than an outer diameter of the spiral blade in the second conveyance path.
 16. The remaining toner conveying apparatus according to claim 15, wherein a distance between an opening facing the image bearing member and the outer circumferential end of the spiral blade in the first conveyance path is set to be 1.3 times or more and less than 2.5 times a radius of the spiral blade in the first conveyance path, and wherein a distance between the opening facing the image bearing member and the outer circumferential end of the spiral blade in the second conveyance path is set to be 0.8 times or more and less than 1.3 times a radius of the spiral blade in the second conveyance path.
 17. The remaining toner conveying apparatus according to claim 14, wherein a separation pitch of the spiral blade in the first conveyance path along a rotation shaft is set to be smaller than a separation pitch of the spiral blade in the second conveyance path along the rotation shaft.
 18. The remaining toner conveying apparatus according to claim 17, wherein the separation pitch in the first conveyance path is set to be in a range of more than 0.5 times and 0.9 times or less the separation pitch in the second conveyance path.
 19. The remaining toner conveying apparatus according to claim 14, wherein an inclination angle of the spiral blade in the first conveyance path with respect to a plane perpendicular to a rotation shaft is set to be smaller than the inclination angle in the second conveyance path.
 20. The remaining toner conveying apparatus according to claim 19, wherein the inclination angle in the first conveyance path is set to be smaller in a range of 2° or more and less than 5° than the inclination angle in the second conveyance path.
 21. The remaining toner conveying apparatus according to claim 12, wherein the conveying portion is configured such that a conveying speed of the developer in the first conveyance path is a speed for convecting the toner introduced by the introducing portion and polishing the surface of the image bearing member.
 22. An image forming apparatus comprising: the image bearing member; and the remaining toner conveying apparatus according to claim
 12. 23. An image forming apparatus comprising: an image bearing member capable of bearing a developer image on a surface of the image bearing member; an introducing portion configured to introduce a developer remaining on the image bearing member without being transferred; and a conveying portion configured to convey the developer introduced by the introducing portion toward a discharge portion, wherein in the conveying portion, a conveying capability of conveying the developer in a first region facing a region where a developer image of the image bearing member is formed is less than the conveying capability in a second region located in a downstream side of the first region in a conveyance direction of the developer, and wherein the developer in the first region can slide on the surface of the image bearing member. 